In combustion engines of the type referred to above, an electric fuel pump draws fuel from a tank and forces this fuel into the lines which lead to the injection valves. Each cylinder of the engine is provided with its own injection valve which injects fuel under high pressure into the intake pipe of the engine or into the inlet channel. Such a gasoline injection system is described in the publication entitled "Bosch Kraftfahrtechnisches Taschenbuch", 19th edition, 1984, pages 366 to 373.
In these injection systems, the danger is present that fuel can reach the intake pipe from the pressure store when the engine is shut off and when the injection valves leak. For the next start of the engine, this condition can lead to a mixture which is excessively rich, to start misfires or to an extended starting operation while at the same time leading to high emissions of toxic materials.